Circuit for electric discharge devices



Dec. 16, 1941. -H, CAMPBELL 2,266,619

CIRCUIT FOR ELECTRIC DISCHARGE DEVICES Filed Oct. 5, 1939 Figlf lr-lve'ntor;

John l-LCampbell,

. His Attorney.

Patented Dec. 16, 1941 CIRCUIT FOR ELECTRIC DISCHARGE DEVIC John H. Campbell, Cleveland Heights, Ohio, assignor to General Electric Company, a corporation of New York Application October 5, 1939, Serial No. 298,082

Claims. (CL 176-124) My invention relates to gaseous electric discharge devices generally, and more particularly to circuit arrangements for starting and operating such devices. Still more particularly, my invention relates to circuit arrangements comprising two or more such devices.

One of the objects of my invention is to provide a starting and operating arrangement for gaseous electric discharge devices provided with thermionic electrodes which employs a minimum of equipment and assures reliable starting together with operation at high efliciencies. An-

other object is to provide a simplified circuit a portion of a novel combination thermal switch and ballasting device which may, if desired, be employed in the circuit; and Figs. 3, 4 and 5 are diagrammatic representations of modified circuit arrangements included within the scope of the present invention.

Referring to Fig. 1, the circuit illustrated therein comprises a plurality (two, in this instance) of gaseous electric discharge devices It, l0- electrically connected in series with each other and with a ballast resistance ll. across the terminalsl2, l3 of a source of alternating or direct current; The devices In, ll) may be positive column discharge lamp devices comprising the elongated tubular envelopes or containers I4, H having sealed into the ends thereof the thermionic electrodes l5, l6, l5, 18' each herein illustrated as consisting of a coil (preferably a coiled-coil of wire such as tungsten coated with a material of high,electron emissivity, such as an alkaline earth oxide like barium or strontium oxide or mixtures thereof). If desired the said electrodes may be so designed that the voltage drop thereacross exceeds the ionizing voltage of the gaseous atmosphere .so that a local arc discharge is formed thereacross during starting, as disclosed in Patent 2,103,034, G. E. Inman. The envelopes l4, ll

ture of gas and vaporizable metal. If desired,

each of the devices l0, It may be a low-pressure positive column lamp of the fluorescent type recently made commercially available wherein the envelope is coated internally with asuitable luminescent material and contains a filling of rare gas, preferably argon, at a low pressure of the order of l-10 mm. of Hg, preferably about 4 mm., and a small quantity of mercury. The ballast resistance ll may, as illustrated, consist of an incandescent tungsten filament lamp.

In accordance with my invention, the lamps I0, H) are initially shunted by the switches l1, H which may be of any suitable type,'either manually or automatically operable and when an envelope about eighteen inches long and one and one-half inches in diameter, containing argon at a pressure of about 4 mm., and a small quantity of mercury. of coiled-coils of tungsten wire coated with a mixture of barium and strontium oxides. The ballast resistance H was a standard commercial watt, volt tungsten filament incandescent lamp. The switches H, H were of the thermal bimetallic type fully described in application Serial No. 228,365, filed September 3, 1938, by Leo R. Peters and assigned to the assignee of the present application, the heaters for the The switches being in series with lamp ll. current' source l2, l3 was a commercial 115 volt, 60 cycle alternating current line.

In the operation of the circuit. when voltage is applied to the line the two switches l1, l1 are closed and current flows through the cathodes of both lamps thereby beating them, the said cathodes and ballast lamp ll all being'connected in series across the line terminals l2, I3, as will be apparent from an inspection of Fig. 1

For convenience in explaining the operation, let

it be assumed that switch I! opens first. When said switch I 1 opens, the current flowing through the series circuit is suddenly reduced to zero The electrodes consisted and with it the voltage drop across the ballast lamp Ii likewise reduces. Thus, the full line voltage is applied to lamp l causing an arc discharge to strike therein between its electrodes l5, l6, and the current through the circuit momentarily increases due to the negative resistance coeilicient of the lamp Hi. This action further raises the temperature of the electrodes I, it of lamp l0 and effectively reduces its a e -61o switches ll, ll comprises a duplicate pair of bimetallic strips l0, l0 and l0, l9 respectively,

the curved strips l0, it being actuated by a single heater or filament H which corresponds to the ballast lamp l of Fig. 1. The said switches ll, ll, as illustrated, are each of the type disclosed and claimed in application Serial No. 228,365,'filed September 3, 1938, by Leo R. Peters and assigned to the assignee of the present apused at I I.

In Fig. 2 is shown a combined switch and ballast unit which may be employed-in the Fig. 1 circuit to combine in one small unit the switches H and I7 and the ballast H.

Each of the 75 required starting voltage. Thus when switch plication. The said bimetallic elements l8, l9 ll opens, the lamp 10 starts, in this case, at and l3. l0 and heater ii are supported from 2. approximately 60 per cent of its normal starting glass stem 20, and are sealed in a glass or metal voltage. (This explanation also holds for direct bulb or envelope (not shown) filled with a suitcurrent operation.) With both lamps l0 and able gas, such as helium or hydrogen, and preferl0 operating, the lamp H acts .as a ballast to ably carrying a base (not shown), such as the limit the current flowing in the circuit. When type employed on radio tubes and having six the line voltage is low, the resistance of the prong contacts thereon. The respective prongs ballast lamp II is automatically decreased and are connected by conductors 2|, 22 to elements as the voltage rises, the resistance increases, l8, l0 respectively, of switch ll; by conductors thus afiording an automatic regulation of curgo 2|, 22 to elements l8, l9 respectively, of switch rent over wide voltage ranges. l1; and by conductors 23, 24 to opposite ends The following is a table of measurements taken of the heater i. The connections in this case during operation of the above lamps: are the same as those shown in Fig. 1. That is,

- Lamp Overall Lamp 53R; BEES tilt till? 3521 53 ggggg; ggggg; till? The voltage drop across the lamps l0, l0 gradthe conductors 2|, 22 to switch ll are connected 'ually increases as the line voltage decreases. At across the cathodes l5, ii of lamp I0; the con- 100 line volts,'the total lamp drop was 95 volts. ductors 2|, 22 to switch H are connected across The lamps will no longer be maintained in opthe cathodes l5, l6 of lamp l0; and the conduceration at line voltages below 100, but will start tors 23, 24 to heater II are connected between at 100 volts. Thus, ballasting can be obtained the terminal'l2 and cathode l5 of the lamp H). with this circuit with a diiference between line 40 The operation of the Fig. l circuit containing the and lamp volts of only five per cent. device shown in Fig. 2 is precisely as described It will be obvious that more than two lamps above. may be operated on this circuit, the limiting fac- The device shown in Fig. 2 has the advantages tors being lamp and line volts. It is necessary, that it makes possible the operation of two or of course, that the combined voltage drops of the more lamps from one auxiliary the size of a small lamps during operation do not exceed the line or radio tube, it will operate on either alternating source voltage. However, in the example specior direct current, it assures a high overall power fically illustrated above, the starting voltage of factor because resistance is the only element in each of the lamps is about 100 to 120 volts, dethe ballast, and it is noiseless in operation. pending to a large extent upon how hot the cath- The-circuits shown in Figs. 3-5 represent modiodes are heated and therein lies an important adflcations which may be made in certain cases to vantage of this circuit. Although, the starting take care of such things as Changes in Vo e. voltage of each lamp must be less than the line e Shape and lamp lengthvoltage, the combined starting voltages may be Referring to Fig. the circuit illustrated e econsiderably higheriin the example nearly twice in is a modification of the 1 Circuit in t as high). Thus it is possible to start and operinsertion of an inductance or choke coil 25 in ate a plurality of lamps whose combined starting es with a p in a in addition to t e voltages are greatly in excess of the line voltage, ballast resistance or lamp H. The source I2, l3 whereas a similar circuit employing a single lamp y, as in be alternating direct whose starting voltage was higher than the line rent- The P p O the inductance 5 s voltage would be inoperative, provide a partial ballast of the lampswhich ef- In place of thermal switche of th type 11 fectively reduces the watts loss over a pure reclosed in the above-mentioned Peters application, 51511841106 ballast as Shown in Such an glow-type thermal switches of the type disclosed dition of reactance to the circuit may be necesin application Serial No. 289,897, filed August 12. e5 a r the Operation of s me d s r e a p 1939, by W. C. Smitley, may be employed. In and will improve the current and voltage wave this case one of the switches is shunted by a P l high resistance (2,000 ohms, for example) since In the 4 Circuit, designed r Operation the switch contact are normally open. T0 at. from a source l2, l3 of alternating current, inplicate the results given above, a watt lamp is 70 ductance 25 is substituted as the ballast for resistance ll of Fig. l, and resistances or lamps 26, 26' are'inserted in series with the switches l1, ll respectively, across lamps l0 and I0. In-some cases "there the line voltage is considerably higher than volts, as for example 220 volts,

and the cathodes I 5, it are of the same resistance as those in the Fig. 1 lamps, it will be necessary to place such resistances 26 and 26' in series with the switches to control the flow of current during the starting cycle. After the lamps I and I0 have started, switches ll andll' are open and the resistances 26 and 26' are out of thecircuit. The ballast need not be a single choke as shown at 25, but may be a pure resistance or lamp ballast as shown in Fig. 1, or a combination of the two as in Fig. 3.

The Fig. circuit is like that shown in Fi 1 2. In combination a plurality of gaseouselectric discharge lamps each having an electrode at except that inductances or choke coils 21, 21' are inserted in series with the switches II, II, respectively, across lamps l0 and III. This arrangement is particularly eifective where the starting voltages of the lamps l0 and Ill are higher than those of the lamps in Fig. 1, the choke coils serving to produce a voltage surge when the switches 11 and II are opened so as to start the lamps. This circuit is also effective for starting a single lamp I0 or Ill whose starting voltage is higher than that of either lamp it or Id of Fig. 1, but whose operating voltage is about the same as the combined operating voltages of lamps Ill and I0 of Fig. 1.

'While I have shown and described above certain forms of my invention, it will be obvious to those skilled in the art that various changes may be made therein without departing from the spirit of the present invention. If desired, the directly heated electrodes l5, it may be replaced by indirectly heated electrodes wherein the said coils it, it serve as heaters for a surrounding metal (nickel) tube which is electrically connected at one end to one end of the said heater, and is coated with electron emissive material. Moreover, for operation from a source of direct current, only one of the electrodes l5 or I 6 need be a thermionic electrode.

What I claim as new and desire to secure by Letters Patent of the UnitedStates is:

1. In combination, a plurality of gaseous electric discharge devices having therein spaced electrodes, one electrode at least in each device being thermionic and adapted to be heated by the passage of current therethrough prior to the starting of the devicefballasting means having a' positive nonlinear resistance temperature characteristic and having low heat inertia, means connecting said devices and ballasting means in a series circuit, and a time delay starting switch for, each of said devices each switch being connected across one of said devices and in series with the thermionic electrode thereof, and means for causing said switches to open successively each end thereof adapted to be heated by the passage of current therethrough prior to the starting of a discharge in the lamp, ballasting means comprising a resistor having a positive nonlinear resistance temperature characteristic and having low heat inertia, means connecting said ballasting means and said lamps in a series circuit, a plurality of starting switches one for each of said lamps each switch being connected across its respective lamp and in series with the electrodes thereof, and means by which said switches are opened in succession and with a time delay after the energization of said circuit. 1

3. In combination a plurality-of gaseous electric discharge lamps each having an electrode at each end thereof adapted to be heated by the passage of current therethrough prior to the starting of a discharge in the lamp, ballasting means comprising a tungsten filament incandescent,

a. In combination, a plurality of electrlcdis charge devices having therein spaced electrodes adapted to be heated by the passage of current therethrough prior to the starting of the device, ballast for said devices, means connecting said ballast and said electrodes in a series circuit, and a starting switch having'a plurality of pairs of contacts, each pair being connected to interrupt said series circuit between the electrodes of a separate device, said switch having common operating means for said pairs of contacts constructed to operate them in sequence. '5. In combination, a plurality of electric discharge devices having therein spaced electrodes adapted to be heated by the passage of current therethrough prior to the starting of the'device, a ballasting resistor, means connecting said resistor, said devices and the electrodes thereof in a series circuit, and a multiple switch having one pair of contacts connected to interrupt said series circuit between the electrodes of one device, and having another pair of contacts connected to interrupt said series ci cuit between the electrodes of the other device, and a single member operative to cause said pairs of contacts to open in sequence.

JOHN H. CAMPBELL. 

